In celebration of our 1000th episode, we're wrapping our heads around big numbers. Educational neuroscientist Elizabeth Toomarian talks about why humans' evolutionarily-old brains are so bad at comprehending large quantities–like the national debt and the size of the universe–and how to better equip ourselves to understand important issues like our finances and the impacts of climate change.Interested in other ways our brains make sense of the world? Email us at shortwave@npr.org.